This disclosure relates to a method for increasing the intrinsic safety of an arrangement for rotational speed detection and/or for the intrinsically safe detection of linear and/or rotational movements of a body, in particular of a wheel, the arrangement comprising a magnetic encoder (5, 25) and a sensor (26). The sensor (26) having at least two sensor elements (S1, S2) which are magnetically coupled to the magnetic encoder (5, 25). The arrangement providing for the intrinsically safe rotational speed detection and/or for the intrinsically safe detection of linear and/or rotational movements of a body, such as a wheel, and to the use of the method and/or of the arrangement in motor vehicles.
It is known to detect the rotational speed of a wheel by means of a sensor arrangement having a magnetic encoder, which rotates with the wheel, and at least one magnetic-field-sensitive sensor, the magnetic encoder being magnetically coupled to the magnetic-field-sensitive sensor via a magnetic air gap.
Sensors, in particular active sensors, based on magnetoresistive effects are used in industry, and particularly often in the motor vehicle industry, owing to their robustness and good signal quality. These good signal properties are ensured, moreover, for example by complying with the tolerances of a specified relative position between encoder track and sensor, in particular the sensor element/elements thereof, upon installation or upon mounting of the sensor. If, by way of example, the tolerances are not complied with as a result of lateral relative offset and a situation of excessively great proximity (excessively small air gap length or excessively strong transverse components of the encoder field strength), signal disturbances can occur which temporarily or permanently alter the sensor output signal in an impermissible manner. The profile of the output signal then no longer corresponds precisely to the movement profile of the pole pairs of the encoder track, rather there typically occur sporadic or permanent frequency multiplications and/or frequency fluctuations, in particular frequency doublings, which can for example also occur in the case of the wheel rotational speed sensors of motor vehicles. In order to avoid such disturbing frequency doublings or frequency multiplications, suitable final acceptance tests are carried out. In order to be able to react appropriately to such phenomena during operation, usually complicated plausibility calculations are carried out. These errors can also become apparent and even be amplified in the course of further signal processing.
Document DE 199 06 937 A1 proposes a rotational speed sensor, the angular pitch of the encoder being coarser than the angular resolution of the rotational speed sensor, and the rotational speed sensor having two magnetic field sensors which are arranged separately from one another and which generate two measurement signals which are phase-offset relative to one another and which are combined in such a way that the output signal has an increased frequency relative to the measurement signals for the purpose of achieving the necessary measurement resolution. Such a rotational speed sensor serves principally for improving the resolution. However, no improvement is achieved with regard to the intrinsic safety of the rotational speed sensor.
The present disclosure includes a method for increasing the intrinsic safety of an arrangement for the rotational speed detection and/or for the intrinsically safe detection of linear and/or rotational movements of a body, in particular of a wheel, and a corresponding arrangement.
The a disclosed method provides for increasing the intrinsic safety of an arrangement for detecting linear and/or rotational movements of a body, in particular of a wheel. The arrangement comprising a magnetic encoder (5, 25) and a sensor (26) with the sensor (26) having at least two sensor elements (S1, S2) which are magnetically coupled to the magnetic encoder (5, 25). The arrangement further provides for the intrinsically safe detection of linear and/or rotational movements of a body, in particular of a wheel, comprising a magnetic encoder (5, 25) and a sensor (26), the magnetic encoder (5, 25) moving and/or rotating with the body, in particular the wheel, and being magnetically coupled to at least two sensor elements (S1, S2) of the sensor (26) via a magnetic air gap.